下伏基岩堆积体边坡抗滑桩加固前后地震响应特征离心模型试验

 为研究抗滑桩加固上覆堆积体--下伏基岩二元结构边坡的抗震机制，开展2组1∶50比尺的离心振动台模型试验，以对比分析下伏基岩堆积体边坡在抗滑排桩加固前后的地震响应特征与抗滑桩的桩身弯矩分布规律。试验时，输入4级加速度峰值连续增大的El Centro波，监测边坡模型坡面与坡体内的加速度响应、坡顶沉降变形以及抗滑桩上静、动弯矩的分布。试验结果显示由于抗滑桩抑制了上覆堆积体的下滑，坡顶的加速度峰值(PGA)放大系数、加速度反应谱以及竖向沉降变形均有不同程度的降低。抗滑桩一方面加固了上覆堆积滑体另一方面在坡体内产生了地震波的反射叠加效应，使得边坡水平响应加速度放大系数出现了桩前增大桩后减小的现象。下伏基岩堆积体边坡坡顶沉降与Arias烈度在抗滑排桩加固前后均具有良好的正相关线性关系。地震荷载作用过程中抗滑桩动力响应弯矩变化幅值明显大于地震作用后的静弯矩增量，且静弯矩与动弯矩变化幅值的分布均在基岩面附近达到峰值，易在基岩面附近造成抗滑桩的破坏，类似工况下抗滑桩的抗震配筋设计应充分考虑这一特点。

Centrifuge modeling tests on seismic response of lower bedrock deposit slopes before and after reinforced with stabilizing piles

In this research，two centrifuge shaking table model tests with the geometric scale of 1∶50 were conducted to study the seismic behaviours of lower bedrock deposit slopes before and after reinforced with stabilizing piles. 4-stage seismic waves(El Centro wave) with the increasing peak acceleration were applied from the bottom of each model. The acceleration response at slope surface and inside，the crest settlements，the distribution characteristics of static and dynamic bending moments were monitored in the process of tests. The recorded data and observations of the centrifuge models showed that the PGA amplification coefficient，the acceleration response spectra and the settlements at slope crest were decreased to some extent when the lower bedrock deposit slope was reinforced with the stabilizing piles. The stabilizing piles improved the seismic performance of upper deposit under earthquake conditions and in the meantime caused the seismic wave reflection effects in slope body，which make slope surface acceleration amplification factor increased along the pile-crest direction but decreased along the pile-toe direction. The relationships between the permanent displacements at slope crest and the Arias intensity of input seismic waves were linear. The changing amplitude of the dynamic bending moment of pile in the earthquake loading process was significantly larger than the increment of static bending moment after seismic excitations. Both the dynamic bending moment and static bending moment of pile reached their peak values near the bedrock surface，where the stabilizing piles most likely been damaged. These features should be fully considered in the aseismic design of stabilizing piles.